The TV Licensing authority has said it is confident "most people will simply obey the law" and stressed it will not implement "mass surveillance techniques" to monitor those using BBC iPlayer.
On Thursday September 1 a loophole that allowed viewers to catch up with shows on BBC iPlayer was closed, meaning that anybody wishing to use the on-demand service must now confirm they have a TV licence.
Previously, only live content streamed on the service was covered by the £145.50-a-year licence fee, while those watching shows on catch-up could do so free of charge.
It had not previously been disclosed how the TV Licensing body would implement the changes in legislation, although there were rumours of snooping on people's TV-viewing habits via private wi-fi connections.
A TV Licensing spokesman denied these rumours, telling the Press Association: "We expect most people will simply obey the law. We are not going to use mass surveillance techniques, we are not going to ask internet providers for IP addresses, and in fact we will simply use existing enforcement processes and techniques which we believe to be adequate and appropriate.
"Our current procedures enable us to catch those watching on devices other than televisions."
In the future, viewers who wish to use BBC iPlayer will be asked if they have a licence and be told "it's the law" to have one before proceeding.
After being told about the changes, they will then have the option to either confirm they are licensed, find out more information about the changes, or buy a licence from the official TV Licensing website.
Viewers now risk prosecution and a £1,000 fine if they download or watch programmes on iPlayer without a TV licence on any device.
Last year the BBC announced a £150 million shortfall in licence fee income for 2016/17, saying there had been a faster-than-predicted fall in the percentage of households owning televisions because of people viewing through catch-up.
The Government committed to closing the loophole, with John Whittingdale, then culture secretary, saying in March: "The BBC works on the basis that all who watch it pay for it.
"Giving a free ride to those who enjoy Sherlock or Bake Off an hour, a day or a week after they are broadcast was never intended and is wrong."
The Government set out plans to update licence fee legislation, as part of negotiations which saw the corporation agreeing to cover the cost of free licences for the over-75s.
People who already have a TV licence will not be affected by the change and viewers will not need a TV licence to download or watch programmes on demand from other providers, such as YouTube, Netflix, ITV Hub, All 4 or Demand 5.